17 / 03 / 2013

A nocturnal sting by a nocturnal wasps!

Apoica flavissima, a night wasp, gives one of the most painful sting in the animal kingdom, and may give a cold that could last several days.

Écoutez cet article 

This huge nest of night wasps was just on the side of the trail. It was in the middle of the dry season in the Veadeiros da Chapadas National Park (Brazil), in the dry habitat of the Cerrado. We were walking in group, made up of students and researchers. Breno Freitas, a brazilian researcher who works in crop pollination, warns me that these wasps are very dangerous. He takes a picture far from the nest, but this isn’t enough for me: I need to be closer. I wish to be able to take a close-up of these marvelous wasps. Some wasps begin to activate and they beat their wings faster, as a sign of warning. This means I am too close, so I decide to retreat slowly while keeping an eye on the nest. Then, Favizia de Oliveira, a bee taxonomist, comes closer and tells me that not only the pain of the sting is unbearable but it can give you a cold that can last up to two weeks. Furthermore, when you get stung, the venon will attract immediately the rest of the colony. I may have avoided a nightmare, however, this discovery intrigued me, I couldn’t let this pass.

The next day, I went back to the nest :

 

Earlier that day, an empty nest was found in the middle of a trail greatly exposed to the sun light. Normally, a fertile female (queen) will fund a colony away from the light, underneath a tree branch where there is enough shadow to avoid any possible overheating of the nest.  Unlike the Vespinae, this species of Polistinae (Epiponini) builds open nest in which we can clearly see the cells. The tree that was housing the old colony probably suffered of drought and lost his leaves. The nest overheated and the larvae baked into their own cells.

Cerrado, Brazil

Figure 1: Ci-haut, l’habitat sec du Cerrado, Brésil; En haut à droite, un nid vacant; En bas à droite, aucun danger de se faire photographié à côté d’un nid vide.

 

You must know that this species struggles to keep a stable temperature in its nest. Indeed, the temperature varies rarely within the cells. Workers cover their nest, head towards the rim, in goal of keeping the cells safe as well as keeping an optimal temperature for the larvae. Furthermore, the top is built so that the heat from sun rays is not conducted into the cells. In fact, thousands of vegetal curled hair are harvested and neatly agglomerated to the rest with the aid of transparent secretion. This creates a fibrous layer which isolates the air inside and helps to avoid heat conduction to the cells.

If these wasps seem calm in the day, you have to wait until sunset to feel the energy that a few hundred individuals can create. Between 5:45 pm and 6:00 pm, the activity is at its climax. At night fall, the workers begin their intensive searching for little insects that will become the delightful meal of their larvae. At 10:00 pm, another period of activity begins. The workers intensify their flight with the nectar of the flowers that bloom in the night, but sometime they are irresistibly attracted to an intense light far off: my light trap (see video below). Disoriented by the intensiveness of the light, they are not resisting towards the collector.

Référence:

FS Nascimento & IC Tannure-Nascimento (2005) Foraging patterns in a swarm foundind wasp, Apoica flavissima van der Vecht (Hymenoptera: Vespidae),Neotrop. Entomol. Vol.34 no.2
Amane S, Mateus S, Hozumi S, Kudô, K, Zucchi R (2009) How does a colony of Apoica flavissima (Hymenoptera, Vespidae, Epiponini) maintain a constant temperature? Entomol Sci 12: 341-345.